DESCRIPTION (provided by the PI): ACE inhibitors are a standard treatment for hypertensive patients. Despite the proven efficacy of these drugs on blood pressure control, there is troubling preliminary data on the safety and effectiveness of these medications in real-world settings, especially among African American patients. Such signals - to date - have not reached the level of evidence required to make it into national guidelines. This application offers a unique opportunity to address this gap in the literature. In a cohort study of patients using data from a clinical data warehouse of 1.8 million patients from New York City's municipal system, we propose to examine potential racial differences in the clinical effectiveness, safety and adverse effects of ACE inhibitors. Our hypothesis is that ACE inhibitors result in adverse clinical outcomes: 1) more often in African Americans compared to Caucasians;2) more often than !-blockers, thiazide diuretics, or calcium channel blockers among nondiabetic African Americans;and 3) the incremental cost-effectiveness of ACE inhibitors will be less than that for other antihypertensives among nondiabetic African Americans.